1. Field of the Invention
The present invention relates to a computer program product, system, and method for a magnetic disk drive using a non-volatile storage device as cache for modified tracks.
2. Description of the Related Art
Computer hard disk drives include one or more disks of magnetic storage medium and a disk drive head assembly to read and write data on the magnetic storage medium. Magnoresistive (MR) heads typically include a write element comprised of a thin film inductive head and a read element comprised of a sensor. MR heads for the disk surfaces of the disk drive are affixed to an actuator or arm that glides across the disk surface to position the head at different track locations. Current is passed to a voice coil motor (VCM) to position the actuator with respect to the disk surface. The amount of torque applied to the actuator is governed by the amount of current in the VCM. The VCM comprises the coil that receives the current and two magnets. During operations, the disk drive components, such as the VCM, can produce vibrations induced as a result of the resonance of the components. Such vibrations may result in undesirable head variations and tracking errors.
Data is stored on the disk surfaces in circular tracks on each disk surface that are thin concentric circular strips on a disk platter surface which comprise the magnetic medium to which data is written by the drive heads. These magnetic strips form a circle and are two-dimensional. In a disk drive system having multiple platters, a cylinder comprises the same circular track number on each platter, spanning all such tracks across each platter surface that is able to store data (without regard to whether or not the track is “bad”). Thus, it is a three-dimensional structure. Any circular track on one disk platter comprising part of a specific cylinder can be written to and read from while the actuator assembly remains stationary. Hard drive manufacturers have increased drive access speed increasing the number of platters which can be read at the same time. The circular tracks on a disk surface are divided into sectors, which are the smallest storage unit on a hard drive.
In the current art, disk diameters are generally maintained at 2.5 inches for laptops and 3.5 inches for desk top systems. Disk drive manufacturers want to reduce the disk diameter to reduce the seek time required to move the write head to different tracks on the disk surface. Further, to reduce latency, the time to rotate the disk to a particular sector, i.e., angular position on the cylinder, disk drive manufacturers increase the rotations per minute (RPMs) of the disks, to levels usually greater than 5400 RPMs. Further, disk drive manufacturers may limit the number of platters of disks to less than five to reduce vibration and other problems resulting from increasing the mass of the spinning disk drives.
There is a need in the art for improved configurations for hard disk drives.